Burrowing apparatus

ABSTRACT

A pneumatic burrowing apparatus comprising a tubular housing with a percussion tip mounted at the leading end of said housing and including a rearwardly directed portion extending interiorly of said housing, said tip being arranged for axial movement relative to said housing. A percussion piston is mounted for reciprocal motion within the housing and arranged to strike said percussion tip to impart a forwardly directed force thereto. Spring means mounted between the percussion tip and the housing are arranged to be compressed therebetween when the tip is driven forwardly by said percussion piston. A displacement cone mounted proximate the leading end of the housing moves forwardly with the housing during a burrowing operation but is loosely slidable relative to said housing when the housing is withdrawn from a burrowed opening.

United States Patent Schmidt Feb. 11, 1975 [54] BURROWING APPARATUS3,559.753 2/197! Meri etal. 173/139 X [75] inventor: Paul Schmidt,Saalhausen, Germany i I Primary E.\'ammerErnestR. Purser l l Asslgnee?Tracto'Techmk Paul Schmldt, Assistant ExuminerRichard E. FavreauSaalhausen' Germmy Attorney, Agent, or Firm-Toren, McGeady and 221Filed: Nov. 17, 1972 s 21 Appl, No.: 307,573

ABSTRACT [30] F i A n i P i i D t 1 1 prneumatie brurrowing apparatuscomprdisingha tIubZ- 18 97 I M57259 ar ousmg wit a percussion tip mounteatt e ea NOV 1 1 German) ing end of said housing and mcludmg arearwardly di- [57] Us Cl 175/19 73/99 173/133 rected portion extendinginteriorly of said housing, i 11/02 said tip being arranged for axialmovement relative to [58] Pic. 73 94 said housing. A percussion pistonis mounted for re- 91 ciprocal motion within the housing and arranged tostrike said percussion tip to impart a forwardly di- [56} Referencescued rected force thereto. Spring means mounted between the percussiontip and the housing are arranged to be UNITED STATES PATENTS compressedtherebetween when the tip is driven for- 955 899 4/l910 Proctor l73/l33X wardly by Said percussion piston A displacement cone #931068 10/1933 fmounted proximate the leading end of the housing g X moves forwardlywith the housing during a burrowing 5 H1960 g S 173/08 operation but isloosely slidable relative to said hous- 311371423 6/1964 ZinEiewi e z.II 173/91 x the housing is Withdrawn from burrowed 3,375,885 4/1968Scott et al 175/94 X p 3,407 884 lO/l968 Zygmunt et al 173/91 3,465.8349/1969 Southworth 1. 175/73 x 23 Claims 12 Drawing Figures ATEHTEU FEB 1I 1975 SHEET 1 BF 6 TQE BURROWING APPARATUS The invention concerns aself-driven, pneumatic burrowing device, in particular for grounddrilling, having a percussion tip and a percussion piston reciprocatingin the housing. Such devices are also known under the designation groundrocket, percussion hammer or percussion drill and serve primarily toinstall supply lines, such as water pipes, electric or telephone linesunder streets or sidewalks without requiring that the pavements or thesidewalks be broken open.

In known devices, the housing of the burrowing apparatus is subjected tovery high loads, so that its life is normally at most 500 hours ofoperation. Moreover, the diameter of such devices is 135 mm and more,although in the practice 50 mm are usually sufficient as diameter forthe bores. The large housing diameter entails high friction, whichgreatly reduces the advance of the device. Furthermore, there is greaterdanger of damage to the street pavement due to cross ripples, becausethe subsoil under streets, already compacted to a large extent, is alsodisplaced upward against the pavement by the advance of the drill, sothat the pavement rises slightly.

Other disadvantages of conventional driving drills reside in the highconsumption of compressed air due to the large pressure surfaces, thedanger of deviation from the desired drilling direction because of thelarge housing diameter, as well as the high production costs resultingfrom the fact that the interior of the housing is worked out of thesolid material.

It is, therefore, the object of the invention to provide a burrowingapparatus which is free from the aforementioned disadvantages and inparticular one which has a longer life than the conventional drills.

According to the invention, this is achieved in that the percussion tipis arranged in the housing of the driving drill and is displaceable inthe axial direction thereof being supported on the housing in theworking direction via a spring member. As a result not only is much lesspercussion energy required than in comparable conventional drivingdrills, but also the load on the housing is greatly reduced. This isattributed to the unique movement conditions effected in the drivingdrill according to the invention. Due to the displaceable arrangementand the elastic support of the percussion tip, the speed with which thepercussion tip is moved after the impingement of the percussion pistonis much greater, and that of the housing much smaller, than inconventional driving drills. Due to the improved advance, a smallerpiston surface can be selected for admission with compressed air, andthe housing diameter can be reduced considerably. The result of this is,besides a great reduction of the frictional resistance in the soil, anappreciable reduction of the production costs.

The present invention will be better understood by reference to thefollowing detailed description of the preferred embodiments thereof,taken in connection with the accompanying drawing, in which:

FIG. 1 shows a longitudinal section through a driving drill according tothe invention;

FIG. 2, is a detailed sectional view of another driving drill accordingto the invention;

FIGS. 3 to 6, are longitudinal sectional views showing equivalentdetails of a third driving drill according to the invention, indifferent operative positions, with a control device;

FIG. 7, is a perspective view of a mount for introducing the drivingdrills according to FIGS. 1-6 into the soil;

FIG. 8, is a sectional view of a driving drill according to theinvention for opening up or widening an existing earth bore;

FIG. 9, shows a side elevation an aiming frame for aligning the drivingdrills;

FIG. 10, is a schematic view showing a driving drill according to theinvention in tandem arrangement; and

FIGS. 11 and 12, are partial views showing in detail steering devicesfor a driving drill according to the invention.

According to FIG. 1, the housing 1 of a driving drill according to theinvention consists of a honed commercial hydraulic tube, chromed forprotection against corrosion and to reduce wear, having an outsidediameter of between -95 mm, and provided at both ends with an internalthread. A bushing 2 is screwed into one end of housing I. In the centerthe bushing 2 has a collar 3 of the same diameter as housing 1, with thecollar 3 being provided with bores 4 to enable engagement by a hookwrench for turning of the bushing 2. The bushing 2 includes externalthreads located axially rearwardly of the collar 3 configured to engagethe internal thread of housing 1.

A threaded porof bushing 2 located axially forwardly of the collar 3 isconfigured to engage a housing front portion 5, which has the samediameter as the collar of bushing 2 and as the housing 1. On its sideopposite the bushing 2, the portion 5 embraces by a collar 6 a pin 7 ofa conical percussion tip 8, which again has the same outside diameter ascollar 3 of bushing 2 and as the housing 1 and which embraces thehousing portion 5 at an offset 9 with a collet 10.

Onto the free end of pin 7 a collar 11 is attached, for example, byscrew threads or the like, which guides the percussion tip 8 in thehousing front portion 5 and which has bores 12 extending axiallyrearwardly thereof to enable engagement by a socket wrench. Betweencollar 6 of the housing front portion 5 and collar ll of the pin 7,there is provided a compression spring 13 held in tension about the pin7 by the collar 11. The adjustable initial tension of spring 13 assuresthat in the starting position shown the percussion tip 8 bears with itshousing-side end face against collar 6 of the housing front portion 5.Direct contact is prevented, however, by an elastic disk 14 arrangedbetween the percussion tip 8 and the housing front portion. All screwedparts are secured against detachment by locking plates.

In operation, by way of an intermediate piston 15 which in the startingposition shown bears against pin 7 of the percussion tip 8, apneumatically moved percussion piston 16 is caused to strike against pin7 of percussion tip 8, so that the percussion tip lunges for ward fromthe housing front portion 5 into the soil. The intermediate piston 15contributes to the crushing, for example of stones which cannot bepushed aside, by the vibrating percussion tip preceeding the housing,and for this purpose it is arranged in bushing 2 for displacement inaxial direction and is supported in bushing 2 by a collar 17 on elasticbuffers 18 arranged in the axial direction before and behind the collar.As the percussion tip 8 lunges forward. the housing 1 follows thismovement under the pressure of spring 13 and of the elastic buffers 18.The buffers 18 are held in the bushing 2 by another collar 19 of bushing2 and by a disk 20 secured in bushing 2 by a spring ring 30. Theintermediate piston 15 forms a sub-assembly with bushing 2 and theelastic buffers 18, as does also the housing tip 5 with the percussiontip 8, collar 11 and plate springs 13. In operation, the condition ofthe spring member formed by the springs 13 is such that the amount ofits compression, in what in the operating direction is the frontmostposition of the percussion tip in the housing, is equal to or smallerthan the maximum permissible amount.

The percussion piston 16 is guided in housing 1 by means of two guiderings 32, 33 arranged at an axial distance from each other on its shell31 and is provided with slide rings 34 at the guide rings 32 and 33 toreduce the friction at housing 1. The guiding of the percussion piston16 with the rings 32 and 33 insures sufficient freedom of movement forthe percussion piston 16 even if housing 1 is twisted to a relativelyhigh degree. Besides, the percussion piston 16 slides with its boredrear end, viewed in the direction of the percussion tip, sealing engagedon a control bushing 35, which is held with a collar 36 in an offset ofthe internal bore of the housing by a sleeve 37 screwed into therespective housing end and having a slightly larger diameter, in theportion protruding from housing 1, than the housing 1.

At the end away from the percussion piston 16, the control sleeve 35 hasa connecting piece 38 designed as a flexible tube for connection to acompressed air line of a compressor (not shown). The compressed aircoming from the compressor passes, in the operative state, through aninternal bore 39 of the control sleeve 35 into the bored end of thepercussion piston 16, so that the percussion piston is accelerated inthe direction of the percussion tip 8. Owing to this, the percussionpiston 16 moves in the housing 1 against the intermediate piston 15. Theair present in housing 1 before the percussion piston 16in the directionof movement-escapes along the generated surface of the percussionpiston. For'this purpose, the percussion piston 16 is provided betweenthe guide rings 33 and 32 at the shell 31 with an external recess whichat the front guide ring 33-in the direction of movement-is connected viaan axial groove 40 with the housing cavity present betweenpercussionpiston 16 and intermediate piston and via a bore 41 in shell31 with a recess 42 at the outer circumference of the control sleeve 35extending as an external opening. However, the connection with recess 42in control sleeve 35 is interrupted by a suitable limitation of recess42 or respectively a suitable arrangement of bore 41 in shell 31 of thepercussion piston 16 approximately after one half of the distancetraveled up to the intermediate piston, and the housing cavity lyingbefore the percussion piston 16-in the direction of movement-is closed.Consequently, if the pressure of the compressed air supplied by thecompressor continues to act at the bored end, there builds up in thehousing cavity before the percussion piston 16 an air pressure whichaccelerates the percussion piston 16 in the opposite direction afterimpingement on the intermediate piston 15 and after transfer of thekinetic energy causing the advance of the percussion tip 8 and of thehousing 1 to the intermediate piston 15. Simultaneously with theimpingement of the percussion piston 16 on the intermediate piston 15,if the length of the control sleeve 35 is adequate, there results viathe bore 41 in shell 31 of the percussion piston 16 a connection of thehousing cavity lying between percussion piston 16 and intermediatepiston 15 with the internal bore 39 of the control sleeve 35, and inaddition to the admission in the bored end the percussion piston ispressurized at the other end with the compressed air coming from thecompressor. As the area at the other endwhich in the working directionof the percussion tip 8 is the front end-is greater than the pressurizedarea at the rear end, the percussion piston 16 returns to its startingposition under the differential pressure of both areas. Before itreaches its starting position, in which the percussion piston 16 bearsagainst collar 36 on the control sleeve 35, there results again aconnection of the housing cavity lying between the percussion piston 16and the intermediate piston 15 with the recess 42 of the control sleeve35 extending externally, so that the air pressure in this housing cavitydecreases and the percussion piston 16 is decelerated by the pressure ofthe compressed air coming from the compressor now acting only in thebored percussion piston end. After reaching its starting position, thepercussion piston 16 is again propelled forward without interruption fora new strike against the intermediate piston 15 at continuedpressurization in the bored end and admission of air to the housingcavity lying before the other end.

The admission of air to the housing cavity via recess 39 in the controlsleeve 35 occurs due to the fact that axially extending bores 43 arepresent in collar 36 of control sleeve 35 and housing 1 is open at whatin the direction of the percussion tip 8 is the rear end, into which thebores 43 open, or respectively that it is provided with a protectivetube 44 of plastic through which air can escape from housing 1 also whenhousing 1 is completely embedded in the soil, and which protectivelyembraces the compressed air line 38 leading to housing 1. The protectivetube 44 is fastened to the housing 1 by a cutting ring screw connection.Specifically the cutting ring screw connection is composed of: a ring 45which is located within the protective tube 44; a ring 46 which extendsexternally about the protective tube 44, is press-fitted with protectivetube 44 into the internal bore of sleeve 37, and in so doing becomesclamped between sleeve 37 and in the outer side of pro tective tube 44;and a cap nut 47 screwed onto sleeve 37, to press the ring 46 with theprotective tube 44 into sleeve 37. Alternatively, a simple clamping ringmay be provided instead of the ring 46, i.e., the protective tube 44 maybe drawn into sleeve 37 while being clamped between the ring 45 and thesimilarly clamping ring which may be additionally slit in the axialdirection.

In the embodiment of the invention according to FIG. 2, the housingfront portion 61 is screwed directly into the housing and comprises apercussion tip 62 in the form of a round chisel, which at the frontend--taken in the working direction-is designed as a hollow chisel by aninward arch equal to the arch of a spherical surface. lntegrally formedat the other end of the tip 62 is a piston 66 and a pin 63. Pin 63 formsthe strike surface for the respective percussion piston and is present,in the starting position shown, in the internal bore of a ring 64 whichis attached, for example by screw threads or the like, with the housingfront portion 61 into the housing 60. Ring 64 limits the movement ofpiston 66 against the working direction of the percussion tip 62. Themovement in the working direction, during which the percussion tip 62 isguided on the one hand directly in the housing front portion 61 and onthe other hand with piston 66 in the housing front portion 61, islimited by an offset 65 of the piston bore formed in the housing frontportion 61 within which piston 66 is slidably movable. During thismovement, the percussion tip 62 is supported on the housing frontportion 61 by way of piston 66 and plate spring 67, which move thepercussion tip 62 back into its starting position from its-in workingdirection in the housing front portion 61frontmost position after eachpercussion.

While in the example according to FIG. 1 the intermediate piston withits elastic suspension insures that the percussion tip 8 does notexecute a movement inadmissible for the plate spring 13 despite a masswhich is small in relation to the mass of the percussion piston 16, i.e.while in FIG. 1 the intermediate piston 15 prevents an inadmissiblecompression of the compression spring 13, an inadmissible compression ofthe plate spring 67 according to FIG. 2 is prevented by the offset 65.

Upon impingement of the percussion piston on pin 63 of the percussiontip 62, the latter, like the percussion tip 8 of FIG. 1, is drivenforward out ofthe housing front portion 61, and via the plate spring 67in the working direction of the percussion tip 62 a pressure is exertedon the housing front portion 61 and on the housing 60. At sufficientspring force of plate spring 67 this pressure is so strong that thehousing 60 with its housing front portion 61 follows the percussion tip62, just as under the pressure of plate spring 13 and of the elasticbuffer 18 the housing 1 follows the percussion tip 8. Otherwise thefriction in the soil, opposing a movement of the housing, and thehousing movement possibly resulting from a previous return of thepercussion piston to its starting position counter to the workingdirection of the percussion tip 62 will be overcome only with theimpingement of the piston 66 on the offset 65 of the housing frontportion. In any case, and in the same manner as the device of FIG. 1, aleading of percussion tip 62 relative to housing front portion 61 and tohousing 60 in the form of a vibratory movement results, which improvesthe advance over conventional driving drills.

Furthermore, the advance according to FIG. 2 is further increased by aring 68 placed on the housing front portion 61, whose diameter is largerthan housing 60 and housing front portion 61. Ring 68 tapers inadaptation to the housing front portion 61 in the working direction ofthe percussion tip 62 and pushes the soil aside so that a bore is formedin the soil whose diameter is greater than the housing diameter, andthat the friction of housing 60 with the soil is considerably reduced.

In order that ring 68 will not hinder a backward movement of housing 60,the seat of ring 68 on the housing front portion 61 is selected so thatit detaches from the housing front portion 61 when, for example in thecase of a bore hole extending in an undesired manner, the driving drillis to be positioned anew and the housing is, for this purpose, movedbackward out of the soil by reversal of the respective percussionpiston.

Further improvement of the advance is brought about by profile grooveswhich, extending crosswise to the longitudinal direction of the housing,largely prevent retraction of the housing 60 during the return stroke ofthe percussion in piston. In this connection, a sawtooth profile, suchas that shown in FIG. 2 on the outer surface of housing 60 with teethpointing backward in relation to the percussion tip, has provedparticularly advantageous.

The reversal of the percussion piston for a backward movement occurs,according to FIGS. 3 to 6, in another driving drill according to theinvention, by means of a cable line 69. Through the cable line 69 asleeve 143 is moved.

The sleeve 143 cooperates with a control sleeve 135, a spring 136, and aring 137. The control sleeve is designed as a tube which is mounted forsliding movement in the ring 137, fastened in the housing and providedwith passage openings 101 for the air escaping from the housing. Ring137 has a sleeve type prolongation 138, in which are present, at twodifferent points, on a circular circumference, a number of radial boresfor balls 139. In the operative position of the control sleeve 135 forbackward running, shown in FIGS. 5 and 6, the balls 139 engage in twoannular grooves 140 and 141 of the control sleeve 135. In the operativeposition for forward running shown in FIGS. 3 and 4, the balls engage ingroove 141 and another annular groove 142 of the control sleeve. By theengagement of the balls 139 the control sleeve 135 is fixed in therespective operative position.

The result of the change of the control sleeve 135 from the operativeposition Forward Running to the operative position Backward Running isthat the period during which the space-in the direction of thepercussion tip-before the percussion piston is pressurized issubstantially shortened, at constant time for a cycle of the percussionpiston, whereas the period during which a pressure difference frombilateral admission with compressed air counter to the direction of thepercussion tip acts on the percussion piston is lengthened accordingly.Thereby the movement of the percussion piston against the percussion tipis decelerated at an early time and possibly an impingement of thepercussion piston on the percussion tip is prevented altogether and themovement of the percussion piston in the opposite direction isdecelerated much less, so that the percussion piston impinges againstring 137 and imparts a backward movement to the housing.

The balls 139 are held in the fixed position by the spring-loaded sleeve143 which slides in the housing of the driving drill. On actuating thecable line 69 to switch from backward running to forward running, sleeveI43 slides from the shown starting position with recesses 144 over theballs 139, which release the balls 139 to the extent that they can justslide out of the annular grooves 140 and 141 when the compressed airsupply is interrupted and spring 136 pushes the control sleeve into theoperative position for forward running. In the operative position forforward running, the fixing of the control sleeve 135 now occursautomatically after release of sleeve 143 by the return thereof into thestarting position, in that sleeve 143 now pushes the balls 139 into thegrooves 141 and 142 of the control sleeve 135. The switching of thedriving drill from forward running to backward running requires anotheractuation of the cable line. Then, at suitable design of the spring 136and with continued supply of compressed air, the control sleeve 135moves back into the starting position shown in FIG. 6 under thecompressed air pressure counter to the spring force.

A protective tube (not shown) may be selectively screwed to the housingend of the driving drill, the screw connection taking place on thesleeve with which ring 135 is clamped in the housing and which isprovided with several grooves extending in axial direction andinterrupting the screw thread for the protective tube. The grooves givethe sleeve the effect of a screw tap, that is, by the grooves theprotective tube can be screwed onto the sleeve without prepared threadand the sleeve cuts into the protective tube with its screw thread. Alsoa so-called wire grip can be used for the attachment of the protectivetube. The protective tubecan moreover be provided with openings and beused for drainage if it remains in the soil.

Besides there is shown in FlGS. 3 to 5 a percussion tip 109 which,though being designed as a hollow chisel like the percussion tipsaccording to FIG. 2 and being mounted displaceably and elastically inthe housing, has a displacement cone 110 with a collet 111 which, likethe collet of percussion tip 8 according to FIG. 1, cooperates with thehousing tip. The displacement cone 110 is mounted on a conicalintermediate piece of the percussion tip 109, and as the cone tapers inthe working direction of the percussion tip 109, it is thereby firmlyconnected in the working direction with the percussion tip withoutadditional aids, while being easily releasable counter to the workingdirection.

In FIG. 7, a mount 75 is shown, with which the driving drill accordingto the invention is introduced into the soil at the beginning of eachdrilling operation and brought into the starting position required for adesired earth drilling. The mount 75 has two jaws 76 and 77 adapted tothe contour of the housing, which receive the housing of the drivingdrill between them and give the housing a position parallel to thelongitudinal axis of the mount. The jaws 76 and 77 are fastened to themount 75 for pivotal movement by means of parallel links 78 and 79, andat the area of contact with the housing they have a greater distancefrom the housing diameter when the parallel links 78 and 79 are in thevertical position or at right angles to the longitudinal axis of themount. Due to the geometry of the parallel links 78 and 79, at eachmovement of the parallel links 78 and 79 out of their vertical positionthe jaws 76 and 77 move toward each other, i.e. they close. Converselythejaws 76 and 77 open when their parallel links 78 and 79 are movedfrom an inclined position into the vertical. Due to an extension spring80 articulated to one parallel link 79, the jaws 76 and 77 always striveto close. This tendency is countered when inserting the housing of adriving drill with a parallel link 79 prolonged in the form of a lever,i.e. the pivoting of the parallel links 78 and 79 by hand counter to theforce of the extension spring 80, required for insertion of a housing,is facilitated by a prolongation of the parallel link 79 and pivoting ofthis parallel link 79. After insertion of the housing and release of theparallel link 79, the jaws 76 and 77 close around the housingautomatically. At the same time, and with a suitable arrangement of theextension spring 80 or insertion of the housing, the jaws 76 and 77 andthe parallel links 78 and 79 move oppositely to the working direction ofthe percussion tip belonging to the housing. After the driving drill hasbeen set in operation, that is, after pressurization with compressedair, the percussion piston moves back and forth in the housing forcesand forces equal in sum act on the housing in each axial direction ofthe housing. As a result of the clamping of the housing between the jaws76 and 77 and their pivotal arrangement, the force acting on the housingin the working direction of the percussion tip leads, with adequatedesign of the extension spring 80, to a pivotal movement of the jaws 76and 77 counter to the force of the extension spring 80. The jaws 76 and77 then open, and the housing slides through between them by itsresidual energy. The force acting on the housing in the other axialdirection, that is, in the pulling direction of the extension spring 80,leads instead to an intensified clamping between the jaws, whichprevents movement. In this respect the jaws 76 and 77 form with theparallel links 78 and 79 a return barrier which, after suffieientanchoring ofthe mount in the ground, insures that the driving drillpenetrates into the soil.

For anchoring in the ground, the mount 75 is connected with a bottomplate 88, which is anchored in the soil with bottom nails 81 beforealignment of the mount 75. For its alignment the mount 75 is pivotedabout a horizontal and a vertical axis. For this purpose mount 75 isconnected with the bottom plate 88 via a cardan joint formed by aturntable 89 arranged for rotary movement on the bottom plate 88 and apivotable suspension of mount 75 in lugs of turntable 89. Afteraligning, i.e. after pivoting about the vertical axis, turntable 89 caneasily be fixed in its pivoted position with an adjusting screw 91. Thesame applies to the pivoting of the mount 75 in the lugs 90, i.e. to thepivoting of mount 75 about the horizontal axis. In this case the fixingis done with screws 92 designed as thumb screws, which also permit anextremely accurate pivoting about the horizontal axis. According to FIG.7, when fixing mount 75 with the thumb screws 92, two thumb screws 92arranged on both sides of the horizontal pivot axis cooperate, bracingmount 75 against the bottom plate 88.

The aligning itself is facilitated by a bubble level, a type of waterlevel, and by a sight 82. The sight 82 includes a rod 83 at eye levelwhich is inserted into the mount 75 perpendicular to the longitudinalaxis thereof and carries at the upper end, on a cross beam 84, a rearsight 85 and a front sight 86 with sighting line parallel to the'longitudinal axis of the mount for sighting a reference point.

Besides, the housing ofthe driving drill rests in mount 75 in the jaws76 and 77 and on a shell type support 87 arranged at a distance from thejaws 76 and 77. The support 87 not only improves the parallel positionof the housing between the jaws 76 and 77, as it reduces the bendingload of the jaws 76 to a negligibly small amount, but it alsofacilitates the insertion of the housing between the jaws 76 and 77 andthe provision of a protective tube embracing the compressed air line tothe housing and possibly the cable line.

FIG. 8 shows a driving drill according to FIGS. 3 to 5 converted for theboring open (widening) of an existing earth bore. According to FIG. 8,instead of the displacement cone a displacement cone is arranged on thepercussion tip 109 and the housing of the driving drill is surroundedwith an additional shell 121. At its tip the displacement cone 120 has acylindrical piece of the same or a slightly smaller diameter than theexisting earth bore. The outside diameter of the displacement cone 120equals that of the shell 121 and determines the diameter of the earthbore during the wid' ening thereof.

Also'for the widening of an existing earth bore exact aligning of thedriving drill is important. There are, however, difficulties in the useof a bubble level when the driving drill must be brought into a certaininclination. Such an inclination can easily be adjusted with an aimingframe 122 shown in FIG. 9. In addition to a sighting device consistingfor example again of a front sight and rear sight, for the sighting of acertain target, the direction finding frame 122 has a plumb line 123 andis set for aligning, with feet 124 adapted to the housing of the drivingdrill, on the housing of the driving drill indicated in dash-dot linesin FIG. 9. By means of a plumb line 123 and a suitable scale, anyposition of the driving drill can then easily be determined.

This is possible also when the driving drill is connected in tandemarrangement according to FIG. 10 with a parallel lying guide body 125.After making a first earth bore, the guide body 125 is connected, forexample by screwing, with the housing of the driving drill, which inFIG. 10 is marked 126, and is introduced into the existing bore with itsfront portion protruding relative to the percussion tip of the drivingdrill, to make a second earth bore, parallel to the first, at the sameoutside diameter as the housing of the driving drill. The driving drillhaving been set in operation, it drills a second bore parallel to thefirst, of the same diameter. The first bore suffers no adverse changedue to the protrusion of the guide body 125 and its length from thedriving drill, i.e. by the displacement work thereof.

For the steering of the driving drill there are provided lastly alsowings 127 or 128 according to FIGS. 11 and 12. The wings 127 aredisposed at any point of the housing of the driving drill lyingdiametrically opposite in pairs, are connected with the housing rigidlyor articulatedly, and steer the driving drill according to itsinclinationto the longitudinal axis of the housing automatically in acertain are through the soil, so that for example traversal beneathstreets of low crown can also be accomplished with the driving drill atsufficient depth without any excavation of earth for positioning thedriving drill. The wings 127 have a form tapering in the workingdirection of the driving drill and are connected with the housing of thedriving drill either rigidly or articulatedly. The articulatedconnection permits the adjustment of the wing inclination to thelongitudinal axis of the housing and hence a selection of the are onwhich the driving drill moves through the earth, or respectively itmakes possible an adaptation to the nature of the ground to betraversed.

The articulated connection of the wings 127 includes a pin 129 fastenedto the housing of the driving drill, on which is mounted for rotarymovement a hub 130 which is welded, for example, to one end of therespective wing 127. In the other end of wing 127 is mounted a trunnionscrew 131, which extends by its trunnion into one of several bores 132arranged in the housing on a corresponding circular circumference aroundthe pivot axis of the wing 127.

Instead of the wings 127 fastened to the housing of the driving drill,or in addition to the wings 127, there may be used for the steering ofthe driving drill a curved stiff protective tube 44a which, like thehousing in FIG. 11, is shown in detail in FIG. 12 and is providedselectively with wings 128. The wings are preferably curved in the sameamount as the protective tube and arranged lying opposite in pairs atthe protective tube, parallel to the longitudinal axis thereof.

What is claimed:

l. Pneumatic burrowing apparatus particularly suitable for earthdrilling comprising a tubular housing including a leading end adapted toact as the anterior of said apparatus during a burrowing operation, apercussion tip mounted in said housing at said leading end and includinga rearwardly directed portion extending interiorly of said housing, saidtip being arranged for axial movement relative to said housing, apercussion piston mounted for reciprocating motion within said housingand arranged to strike said percussion tip to impart a forwardlydirected force thereto, pneumatic means including an energy source forimparting a striking force to said piston, spring means mounted betweensaid percussion tip and said housing and arranged to be compressedtherebetween upon relative movement of said tip forwardly of saidhousing, and a displacement cone mounted proximate said leading end forforward movement with said housing during a burrowing operation, saiddisplacement cone being loosely slidable relative to said housing in adirection forwardly thereof.

2. Apparatus according to claim 1 including an adjustable stop memberaxially displaceable relative to said housing engaging said spring meansfor enabling adjustment of the spring force thereof.

3. Apparatus according to claim 1 including stop means engaging saidpercussion tip to limit movement of said tip relative to said housing.

4. Apparatus according to claim 1 wherein said displacement cone ismounted upon said percussion tip.

5. Apparatus according to claim 1 wherein said displacement cone ismounted upon a portion of said housing proximate said leading end.

6. Apparatus according to claim 1 including profile grooves arrangedupon the outer surface of said tubular housing and extendingtransversely to the longitudinal direction of said housing.

7. Apparatus according to claim 1 including a protective tube attachedto the rear end of said housing taken relative to the working directionof said percussion tip.

8. Apparatus according to claim 1 including a guide body attachablealongside of said tubular housing and extending generally parallelthereto.

9. Apparatus according to claim 1 including steering wings adjustablyattachable to the exterior of said hous- 10. Apparatus according toclaim 1 including a curved stiff protective tube attachable to saidhousing.

11. Apparatus according to claim 1 including an intermediate pistonarranged in the line of action between said percussion piston and saidpercussion tip and being displaceable in the direction of movementthereof.

12. Apparatus according to claim 11 wherein said intermediate piston isresiliently mounted within said housing.

13. Apparatus according to claim 1 wherein said percussion tip is formedas a hollow chisel.

14. Apparatus according to claim 13 wherein said percussion tip isarched inwardly in the form of a spherical cap at the respective endface thereof extending toward the leading end of said apparatus in theworking direction thereof.

15. Apparatus according to claim 13 wherein said percussion tip chiselcomprises a circular cross sectional configuration. wherein saiddisplacement cone is mounted upon said chisel and is arranged at adistance from said chisel tip which is a multiple of the diametraldimension of said chisel.

16. Apparatus according to claim 1 including a control sleeve mountedwithin said housing and having an internal bore designed as a compressedair inlet and being provided at its circumference with at least one airchannel, said percussion piston being hollow at a rear end thereof takenin the working direction of said piston, said piston sliding by itshollow rear end in the space between said control sleeve and the innerwall of said housing and simultaneously forming a seal on said controlsleeve and on the inner wall of said housing, there being provided inthe hollow rear end of said percussion piston an opening which extendsover at least one channel to the front end face of said percussionpiston taken in the working direction thereof, said channelcorresponding during the working stroke of said percussion piston withthe channel in said control sleeve alone and during the return stroke ofsaid combustion piston with the internal bore of said control sleevealone.

17. Apparatus according to claim 16 wherein said control sleeve isdisplaceably arranged within said housing, with the displacement path ofsaid control sleeve being limited by stop means, with a force exerted onsaid housing by said percussion piston in the working direction thereofbeing greater in one fixed position and smaller in another fixedposition than the force ex- 12 erted on said housing in the oppositedirection.

18. Apparatus according to claim 1 including a mounting assembly adaptedto have said burrowing apparatus mounted therein for guiding saidapparatus during a burrowing operation.

19. Apparatus according to claim 18 wherein said mounting device isprovided with a return barrier consisting of two jaws held in a pair ofspring loaded parallel links which are at the areas of contact with saidhousing in a vertical position of said parallel links arranged at adistance from each other which is greater than the outside diameter ofsaid housing.

20. Apparatus according to claim 18 wherein said mounting deviceincludes a bubble level enabling positioning of said mount at adesiredlocation.

21. Apparatus according to claim 18 wherein said mounting deviceincludes an aiming frame with a plumb line device enabling positioningof said mount.

22. Apparatus according to claim 18 wherein said mounting deviceincludes sighting means enabling desired orientation of said mount.

23. Apparatus according to claim 18 wherein said mounting deviceincludes a bottom plate and a cardan joint interconnecting said mountingdevice with said bottom plate, said mounting device being adjustablypositionable relative to said bottom plate to enable fixation thereof inthe earth.

l =l l=

1. Pneumatic burrowing apparatus particularly suitable for earthdrilling comprising a tubular housing including a leading end adapted toact as the anterior of said apparatus during a burrowing operation, apercussion tip mounted in said housing at said leading end and includinga rearwardly directed portion extending interiorly of said housing, saidtip being arranged for axial movement relative to said housing, apercussion piston mounted for reciprocating motion within said housingand arranged to strike said percussion tip to impart a forwardlydirected force thereto, pneumatic means including an energy source forimparting a striking force to said piston, spring means mounted betweensaid percussion tip and said housing and arranged to be compressedtherebetween upon relative movement of said tip forwardly of saidhousing, and a displacement cone mounted proximate said leading end forforward movement with said housing during a burrowing operation, saiddisplacement cone being loosely slidable relative to said housing in adirection forwardly thereof.
 2. Apparatus according to claim 1 includingan adjustable stop member axially displaceable relative to said housingengaging said spring means for enabling adjustment of the spring forcethereof.
 3. Apparatus according to claim 1 including stop means engagingsaid percussion tip to limit movement of said tip relative to saidhousing.
 4. Apparatus according to claim 1 wherein said displacementcone is mounted upon said percussion tip.
 5. Apparatus according toclaim 1 wherein said displacement cone is mounted upon a portion of saidhousing proximate said leading end.
 6. Apparatus according to claim 1including profile grooves arranged upon the outer surface of saidtubular housing and extending transversely to the longitudinal directionof said housing.
 7. Apparatus according to claim 1 including aprotective tube attached to the rear end of said housing taken relativeto the working direction of said percussion tip.
 8. Apparatus accordingto claim 1 including a guide body attachable alongside of said tubularhousing and extending generally parallel thereto.
 9. Apparatus accordingto claim 1 including steering wings adjustably attachable to theexterior of said housing.
 10. Apparatus according to claim 1 including acurved stiff protective tube attachable to said housing.
 11. Apparatusaccording to claim 1 including an intermediate piston arranged in theline of action between said percussion piston and said percussion tipand being displaceable in The direction of movement thereof. 12.Apparatus according to claim 11 wherein said intermediate piston isresiliently mounted within said housing.
 13. Apparatus according toclaim 1 wherein said percussion tip is formed as a hollow chisel. 14.Apparatus according to claim 13 wherein said percussion tip is archedinwardly in the form of a spherical cap at the respective end facethereof extending toward the leading end of said apparatus in theworking direction thereof.
 15. Apparatus according to claim 13 whereinsaid percussion tip chisel comprises a circular cross sectionalconfiguration, wherein said displacement cone is mounted upon saidchisel and is arranged at a distance from said chisel tip which is amultiple of the diametral dimension of said chisel.
 16. Apparatusaccording to claim 1 including a control sleeve mounted within saidhousing and having an internal bore designed as a compressed air inletand being provided at its circumference with at least one air channel,said percussion piston being hollow at a rear end thereof taken in theworking direction of said piston, said piston sliding by its hollow rearend in the space between said control sleeve and the inner wall of saidhousing and simultaneously forming a seal on said control sleeve and onthe inner wall of said housing, there being provided in the hollow rearend of said percussion piston an opening which extends over at least onechannel to the front end face of said percussion piston taken in theworking direction thereof, said channel corresponding during the workingstroke of said percussion piston with the channel in said control sleevealone and during the return stroke of said combustion piston with theinternal bore of said control sleeve alone.
 17. Apparatus according toclaim 16 wherein said control sleeve is displaceably arranged withinsaid housing, with the displacement path of said control sleeve beinglimited by stop means, with a force exerted on said housing by saidpercussion piston in the working direction thereof being greater in onefixed position and smaller in another fixed position than the forceexerted on said housing in the opposite direction.
 18. Apparatusaccording to claim 1 including a mounting assembly adapted to have saidburrowing apparatus mounted therein for guiding said apparatus during aburrowing operation.
 19. Apparatus according to claim 18 wherein saidmounting device is provided with a return barrier consisting of two jawsheld in a pair of spring loaded parallel links which are at the areas ofcontact with said housing in a vertical position of said parallel linksarranged at a distance from each other which is greater than the outsidediameter of said housing.
 20. Apparatus according to claim 18 whereinsaid mounting device includes a bubble level enabling positioning ofsaid mount at a desired location.
 21. Apparatus according to claim 18wherein said mounting device includes an aiming frame with a plumb linedevice enabling positioning of said mount.
 22. Apparatus according toclaim 18 wherein said mounting device includes sighting means enablingdesired orientation of said mount.
 23. Apparatus according to claim 18wherein said mounting device includes a bottom plate and a cardan jointinterconnecting said mounting device with said bottom plate, saidmounting device being adjustably positionable relative to said bottomplate to enable fixation thereof in the earth.